A fired heater is a widely used process furnace in the fields of petroleum, petrochemistry, natural gas and metallurgy. The fired heater is gas or oil-fueled, and the heat carrier materials in the furnace pipe are heated directly by the flame to meet the temperature requirement for downstream equipments.
Currently, the exhaust gas temperature of a fired heater is generally high, normally within the range of 130˜180° C., such that the thermal efficiency of the fuel is usually between 88% and 92%. Compared with a condensing boiler, a fired heater discharges flue gas containing a large amount of unutilized sensible heat and latent heat, causing an indirect waste of fuel, increasing the production cost and exerting a negative influence on the environment. Additionally, the flue gas discharged from the fired heater further contains water vapor, SO2, etc. In discharging the flue gas, the water vapor condenses and dissolves the SO2 to produce sulfurous acid, sulfuric acid, etc, which will corrode the entire exhaust equipment of the fired heater and pollute the environment as well.
In “Analysis of Property of a New Type Heat Exchanger with Ceramics Regenerator and High-frequency Switch by Experiment” (Yan Liang, Huazhong University of Science & Technology, Wuhan 430074, P.R.China, January, 2007), it disclosed a new ceramic regenerative heat exchanger using the high frequency commutation technology, wherein experimental tests on its heat exchange performance and resistance performance were carried out. Yan's experiments showed that the ceramic honeycomb regenerative air preheater could exchange heat between two fluids so as to recover the industrial exhaust heat efficiently. However, when this high frequency commutation ceramic regenerative heat exchanger is applied in a fired heater, where there is a switch between different heat exchange chambers, the furnace pressure and the furnace temperature of the fired heater would fluctuate. Moreover, because of the volume effect of the heat exchange chamber, the residual flue gas therein would re-enter into the fired heater and cause a flameout therein due to a lack of oxygen. These problems severely limit the application of the high frequency commutation ceramic regenerative heat exchanger in the field of the fired heater.